Purpose:
To examine the efficacy and safety of valproic acid (VPA) use in patients with retinitis pigmentosa (RP).

Methods:
A prospective, interventional, non-comparative case study. Twenty-nine eyes from 29 patients with RP whose corrected visual acuities (VA:logMAR) ranged from 1.0 to 0.16 with visual fields (VF: measured with Goldman perimeter with I4) of 10 degrees or less were sequentially recruited. Patients received oral supplementation with 400 mg of VPA daily for 6 months and were further followed for additional 6 months. VA (log MAR); VF (measured with Humphrey Field Analyzer (HFA): the central 10-2 program); the mean retinal sensitivities of four central points (measured with HFA and Micro Perimeter 1) and subjective questionnaires were examined before, during (1, 3 and 6months) and after the cessation of (9 and 12 months) VPA supplementation.

Results:
With VPA intake, mean best-corrected VA (logMAR) significantly improved from 0.494 at the baseline to 0.446 at 3 months and 0.439 at 6 months (p<0.05), and the mean deviation of the VF significantly improved from -26.1 at the baseline to -25.5 at 3 months and -25.4 at 6 months (p<0.05). These efficacies, however, were reversed to the baseline levels after the cessation of VPA intake. Retinal sensitivity of four central points did not change throughout the 12-month study period. While in internal use of VPA, 15 of 29 patients answered “easier to see” whereas blurred vision was registered in 21 of 29 patients on cessation. No systemic drug-related adverse events were observed.

Conclusions:
Oral intake of VPA was suggestive of a short time benefit to patients with RP while in use. It is necessary to examine the effect of a longer VPA supplementation in a controlled study design.